XIII 



lYCOPODlNE^ 



517 



thickened, so that the archegonial tissue of the prothalhum is 

 very sharply separated from the nutritive tissue below. 



Sometime after germination begins, the vacuole completely 

 disappears, and sometimes a spongy-looking mass was seen 

 filling it before it finally disappeared. In the later stages, the 

 nuclei in the cytoplasm immediately below the diaphragm are 

 much more numerous and correspondingly smaller than those 

 in the much more coarsely granular cytoplasm of the basal 

 region. The finely granular protoplasm and numerous nuclei 



Fig. 298. — Selaginella Kraussiana. A, Nearly median section of a fully-developed 

 female prothallium, showing the diaphragm (d) , X180. One of the archegonia 

 has been fertilised, and the suspensor (sus) has penetrated through the diaphragm 

 into the tissue below it; B-E, development of the archegonium, X360; F, two- 

 celled embryo, belonging to the suspensor shown in A, X360; G, end of a sus- 

 pensor with two-celled embryo {em), X360. 



show the region where the cell-formation begins which results 

 in the secondary prothallial tissue. 



Arnoldi ( i ) states that in ^. ciispidata there is a single 

 large primary nucleus near the apex of the spore which is com- 

 pletely filled with cytoplasm. It looks very much, however, 

 as if he had mistaken the protoplasmic vesicle of the young 



